1. In the folder src/bin, create a file called hashset.rs.
2. Add the following code, and run it with cargo run --bin hashset:

1   use std::collections::HashSet;
2 
3   fn main() {
4     // Most of the interface of HashSet
5     // is the same as HashMap, just without
6     // the methods that handle values
7     let mut books = HashSet::new();
8     books.insert("Harry Potter and the Philosopher's Stone");
9     books.insert("The Name of the Wind");
10    books.insert("A Game of Thrones");
11 
12    // A HashSet will ignore duplicate entries
13    // but will return if an entry is new or not
14    let is_new = books.insert("The Lies of Locke Lamora");
15    if is_new {
16      println!("We've just added a new book!");
17    }
18 
19    let is_new = books.insert("A Game of Thrones");
20    if !is_new {
21      println!("Sorry, we already had that book in store");
22    }
23 
24    // Check if it contains a key
25    if !books.contains("The Doors of Stone") {
26      println!("We sadly don't have that book yet");
27    }
28 
29    // Remove an entry
30    let was_removed = books.remove("The Darkness that comes
        before");
31    if !was_removed {
32      println!("Couldn't remove book; We didn't have it to begin 
          with");
33    }
34    let was_removed = books.remove("Harry Potter and the 
        Philosopher's Stone");
35    if was_removed {
36      println!("Oops, we lost a book");
37    }

3. Compare different HashSets:

41    let one_to_five: HashSet<_> = (1..6).collect();
42    let five_to_ten: HashSet<_> = (5..11).collect();
43    let one_to_ten: HashSet<_> = (1..11).collect();
44    let three_to_eight: HashSet<_> = (3..9).collect();
45 
46    // Check if two HashSets have no elements in common
47    let is_disjoint = one_to_five.is_disjoint(&five_to_ten);
48    println!(
49      "is {:?} disjoint from {:?}?: {}",
50       one_to_five,
51       five_to_ten,
52       is_disjoint
53    );
54    let is_disjoint = one_to_five.is_disjoint(&three_to_eight);
55    println!(
56      "is {:?} disjoint from {:?}?: {}",
57       one_to_five,
58       three_to_eight,
59       is_disjoint
60    );
61 
62    // Check if a HashSet is fully contained in another
63    let is_subset = one_to_five.is_subset(&five_to_ten);
64    println!(
65      "is {:?} a subset of {:?}?: {}",
66       one_to_five,
67       five_to_ten,
68       is_subset
69    );
70    let is_subset = one_to_five.is_subset(&one_to_ten);
71    println!(
72      "is {:?} a subset of {:?}?: {}",
73       one_to_five,
74       one_to_ten,
75       is_subset
76    );
77 
78    // Check if a HashSet fully contains another
79    let is_superset = three_to_eight.is_superset(&five_to_ten);
80    println!(
81      "is {:?} a superset of {:?}?: {}",
82      three_to_eight,
83      five_to_ten,
84      is_superset
85    );
86    let is_superset = one_to_ten.is_superset(&five_to_ten);
87    println!(
88    "is {:?} a superset of {:?}?: {}",
89      one_to_ten,
90      five_to_ten,
91      is_superset
92    );

4. Join two HashSets in various ways:

96    // Get the values that are in the first HashSet
97    // but not in the second
98    let difference = one_to_five.difference(&three_to_eight);
99    println!(
100     "The difference between {:?} and {:?} is {:?}",
101      one_to_five,
102      three_to_eight,
103      difference
104   );
105 
106   // Get the values that are in either HashSets, but not in both
107   let symmetric_difference = 
        one_to_five.symmetric_difference(&three_to_eight);
108   println!(
109     "The symmetric difference between {:?} and {:?} is {:?}",
110      one_to_five,
111      three_to_eight,
112      symmetric_difference
113   );
114 
115   // Get the values that are in both HashSets
116   let intersection = one_to_five.intersection(&three_to_eight);
117   println!(
118     "The intersection difference between {:?} and {:?} is {:?}",
119      one_to_five,
120      three_to_eight,
121      intersection
122   );
123 
124   // Get all values in both HashSets
125   let union = one_to_five.union(&three_to_eight);
126   println!(
127     "The union difference between {:?} and {:?} is {:?}",
128      one_to_five,
129      three_to_eight,
130      union
131   );
132 }